The Application Of Individual Trabecular Segmentation Based On Micro-CT Images In Human Osteoporosis And Osteoarthritis

Objective: The morphological changes of plate-rod trabeculae bone and their interconnection mode determine microstructure and biomechanical properties of the cancellous bone.The microstructure and mechanical properties of the bone can be changed during the process of bone reconstruc tion disorder,which can lead to the corresponding bone diseases,such as osteoarthritis and osteoporosis.Therefore,finding the changes of bone microstructure and mechanical properties can provide theoretical support for the pathogenesis of bone disease a nd early diagnosis.Different imaging methods have been developed to visualize bone microstructure in 3D,such as micro computed tomography(?CT)and high-resolution peripheral quantitative computed tomography(HR-pQCT).However,image analysis software of ?CT and HR-pQCT can't find the microstructure characteristics of the rod-plate trabeculae bone.Traditional trabecular bone microstructural evaluation techniques either derive the microstructural parameters in a model-dependent or independent method in a way which does not advance further based on the characteristics of bone architecture.Individual trabecula segmentation(ITS)technique was developed to segment the 3D connected network into individual trabecular plates and rods.This technique fully quantifies the plate-and rod-related microstructural characteristics based on trabecular morphology.ITS can be applied to the trabecular compartment of scans to evaluate the plate-and rod-related microstructural parameters.In this study,Individual trabecula segmentation was applied to common orthopaedic diseases such as osteoarthritis and osteoporosis.(1)To investigate age-related differences in microarchitecture and estimated bone strength at distal radius and tibia using ITS and micro finite element(?FE)analyses in C hinese female population.And to establish age-based normative values for ITS parameters and investigate the influencing factors on bone microarchitecture in Chinese female population.(2)To investigate the trabecular rods and plates microstructure changes in O A subchondral bone using ITS analyses.To explore the possible role of rod-and-plate microstructural changes in the initiation and progression of OA.(3)ITS was used to analyze the rod-plate microstructure differences in subchondral bone between OA and OP hip joint,and to explore their respective pathogenesis.Methods:(1)In a cross-sectional cohort of 361 Chinese women aged 20–89 years,we obtained bone microarchitecture and bone strength at distal radius and tibia using ITS and ?FE analyses.Observed the following parameters: bone volume fraction(BV/TV),Plate bone volume fraction(p BV/TV),Rod bone volume fraction(rBV/TV),Plate bone volume fraction divide Rod bone volume fraction(P-R Ratio),Plate trabecular number(p Tb.N),Rod trabecular number(rTb.N),Mean trabecular plate thickness(pTb.Th),Mean trabecular rod thickness(r Tb.Th),Rod-Rod Junction density(R-R Junc.D),Plate-Rod Junction density(R-P Junc.D),Plate-Plate Junction density(P-P Junc.D),Whole bone stiffness,Estimated failure load,Trabecular stiffness.(2)Tibial plateau specimens were collected from OA patients undergoing total knee replacement surgeries.Control tibial plateaus were harvested from healthy cadaver donors.OA and control tibial plateaus were first scanned by ?CT.According to the extent of cartilage damage,ITS technical was used to analyse 3 anatomic locations(medial cartilage denudation,medial damaged cartilage,lateral intact cartilage).Then tibial plateaus were processed for histology and Immunohistochemistry.Safranin O-Fast Green staining,OARSI-modified manking score were applied to assess the severity of articular cartilage degeneration.Immunohistochemistry was carried out to analyze the expression of TGF-?1,Osteocalcin,Osterix in subchondral bone.(3)The femoral head was obtained at the time of hip arthroplasty from 60 postmenopausal women,30 with OA and 30 with OP.Specimens were first scanned by ?CT.Subchondral trabecular bone(STB)and deeper trabecular bone(DTB)were extracted from the load-bearing region of femoral heads.ITS was performed to assess rod-plate trabecular bone microarchitecture parameters in subchondral trabecular bone and deeper trabecular bone.Results:(1)At both distal radius and tibia,significant negative correlations with age were found for BV/TV,p BV/TV,rBV/TV,P-R Ratio,pTb.N,r Tb.N,R-R Junc.D,R-P Junc.D,P-P Junc.D,whole bone stiffness,trabecular stiffness and estimated failure load(all p<0.001).At the distal radius,the largest age-related difference was found in trabecular stiffness(80.229%)between age of 20 and 89 years,followed by pBV/TV(72.441%),whole bone stiffness(68.073%),P-P Junc.D(67.779%),estimated failure load(66.244%),R-P Junc.D(62.563%),BV/TV(56.350%),r BV/TV(44.368%),P-R Ratio(41.895%),R-R Junc.D(39.007%),p Tb.N(29.438%),r Tb.N(17.074%),r Tb.Th(5.559%).At the distal tibia,the largest age-related difference was found in whole bone stiffness(50.210%)between age of 20 and 89 years,followed by estimated failure load(50.015%),P-P Junc.D(49.867%),p BV/TV(49.134%),trabecular stiffness(48.662%),R-P Junc.D(46.173%),a BV/TV(45.625%),BV/TV(42.521%),R-R Junc.D(37.986%),r BV/TV(32.976%),P-R Ratio(23.879%),p Tb.N(19.611%),r Tb.N(14.960%).(2)OARSI score,BV/TV,Modulus,P-R ratio,p BV/TV,pTb.Th,pTb.N,rBV/TV,r Tb.Th,rTb.N were significantly increased in medial cartilage denudation and medial damaged cartilage OA regions compared to control(all p<0.05).However,r Tb.N was significantly decreased(p=0.013)and p Tb.Th was significantly increased(p=0.028)in lateral intact cartilage OA regions compared to control.The expression of TGF-?1,Osteocalcin and Osterix in subchondral bone were more in articular cartilage degeneration group than that of intact(all p<0.01).(3)In OA patients,BV/TV,p BV/TV,rBV/TV,P-R Ratio,p Tb.N,r Tb.N,R-R Junc.D,R-P Junc.D,P-P Junc.D,Modulus from STB were significantly higher than those from DTB(all p<0.05).In OP patients,BV/TV,p BV/TV,r BV/TV,P-R Ratio,p Tb.N,r Tb.N,R-R Junc.D,R-P Junc.D,P-P Junc.D,Modulus from STB were no difference than those from DTB.BV/TV,pBV/TV,rBV/TV,P-R Ratio,p Tb.N,r Tb.N,R-R Junc.D,R-P Junc.D,P-P Junc.D,Modulus from STB in OA patients were significantly higher than those from DTB in OP patients(all p<0.05).Conclusion:(1)Loss of trabecular bone was already evident in young adulthood and continued throughout life.ITS technical analysis established minutely age-related normative values for bone microarchitecture parameters in Chinese women and provided great significance to the early diagnosis and prevention of osteoporosis.(2)Rod-and-plate microstructural changes in the subchondral trabecular bone play an important role in the development of OA,and that advanced microstructural analysis techniques such as ITS are necessary in detecting these early but subtle changes.(3)The difference in mechanical properties between OA and OP cancellous bone is attributed to different bone structure.